Electromagnetic waves are able to propagate through a waveguide cavity formed between parallel plates. In certain implementations, when a wave propagates multiple times within a cavity, multiple paths are created such that the multiple paths for wave propagation overlap. When the wave paths overlap, the multiple waves constructively and destructively interfere with each other causing peaks and nulls within the signal. When a receiver receives the signal within the cavity, the nulls may cause signal dropouts that reduce the reliability of a communication link. For example, in a digital communication system the signal dropouts cause errors that increase the bit error rate above a desired threshold.